Question: Determine how many solutions exist for the system of equations. ${4x-y = 10}$ ${-4x+y = -10}$
Solution: Convert both equations to slope-intercept form: ${4x-y = 10}$ $4x{-4x} - y = 10{-4x}$ $-y = 10-4x$ $y = -10+4x$ ${y = 4x-10}$ ${-4x+y = -10}$ $-4x{+4x} + y = -10{+4x}$ $y = -10+4x$ ${y = 4x-10}$ Just by looking at both equations in slope-intercept form, what can you determine? ${y = 4x-10}$ ${y = 4x-10}$ Both equations have the same slope and the same y-intercept, which means the lines would completely overlap. ${1}$ ${2}$ ${3}$ ${4}$ ${5}$ ${6}$ ${7}$ ${8}$ ${9}$ ${\llap{-}2}$ ${\llap{-}3}$ ${\llap{-}4}$ ${\llap{-}5}$ ${\llap{-}6}$ ${\llap{-}7}$ ${\llap{-}8}$ ${\llap{-}9}$ ${1}$ ${2}$ ${3}$ ${4}$ ${5}$ ${6}$ ${7}$ ${8}$ ${9}$ ${\llap{-}2}$ ${\llap{-}3}$ ${\llap{-}4}$ ${\llap{-}5}$ ${\llap{-}6}$ ${\llap{-}7}$ ${\llap{-}8}$ ${\llap{-}9}$ Since any solution of ${4x-y = 10}$ is also a solution of ${-4x+y = -10}$, there are infinitely many solutions.